Re: [RFC LINUX PATCH] Dcoumentation: dt: mailbox: Add Xilinx IPI Mailbox

From: Sudeep Holla
Date: Fri Sep 22 2017 - 07:10:18 EST


On Fri, Sep 22, 2017 at 06:05:18AM +0000, Jiaying Liang wrote:
>
> Xilinx ZynqMP IPI(Inter Processor Interrupt) is a hardware block in ZynqMP
> SoC used for the communication between various processor systems.
>
> Signed-off-by: Wendy Liang <jliang@xxxxxxxxxx>
> ---
> .../bindings/mailbox/xlnx,zynqmp-ipi-mailbox.txt | 88 ++++++++++++++++++++++
> 1 file changed, 88 insertions(+)
> create mode 100644
> Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.txt
>
> diff --git a/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-
> mailbox.txt b/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-
> mailbox.txt
> new file mode 100644
> index 0000000..5d915d1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.
> +++ txt
> @@ -0,0 +1,88 @@
> +Xilinx IPI Mailbox Driver
> +========================================
> +
> +The Xilinx IPI(Inter Processor Interrupt) mailbox driver is a mailbox
> +controller that manages the messaging between two IPI agents. Each IPI
> +mailbox has request and response buffers between the two IPI agents.
> +
> ++-------------------------------------+
> +| | Xilinx ZynqMP IPI Mailbox
> +| Controller|
> +| |
> +| +-------------+
> +| | SMC |
> +| | |
> ++--------+--------------+------+------+
> + | |
> + | +-----------------+
> + | | ATF (ARM trusted firmware)

I suppose it should work with any EL3 firmware, ATF reference can be
removed IMO.

> + | |
> ++-------------------------------------+
> + | | Hardware
> + | |
> + +--------------------------------------+
> + | |
> + +----------------------+ +-----------+ |
> + | | Buffers between | | IPI Agent | |
> + | | two IPI agents | | Registers | |
> + | +--------------------+ +-----------+ |
> + | |
> + | Xilinx ZynqMP IPI |
> + +--------------------------------------+
> +
> +
> +Message Manager Device Node:
> +===========================
> +Required properties:
> +--------------------
> +- compatible: Shall be: "xlnx,zynqmp-ipi-mailbox"
> +- ipi-smc-fid-base Base offset of SMC function IDs for IPI mailbox SMC.
> + It contains the IPI IDs of the two IPI agents.

Why is "SMC" associated with this hardware block ? Is it secure device ?
Can Linux access it ? If so, why do you need SMC ?

> +- reg: IPI request and response buffers address range. It
> + can be the IPI buffers from the hardware or it can
> + be carved out shared memory.

It sounds like buffer used for communication and not part of this IP.
Shouldn't this be part of mailbox client binding rather than controller
binding.

> +- reg-names: Reg resource name of the IPI request and response
> + buffers.
> +- #mbox-cells: Shall be 1. Contains the logical channel IDs of the
> + channels on the IPI mailbox.
> +- interrupt-parent: Phandle for the interrupt controller.
> +- interrupts: Interrupt mapping.
> +
> +Required properties:
> +--------------------
> +- method: The method of accessing the IPI agent registers.
> + Permitted values are: "smc" and "hvc". Default is
> + "smc".
> +Example:
> +------------
> + /* APU IPI mailbox driver */
> + ipis {
> + #address-cells = <1>;
> + #size-cells = <0>;
> + ipi_mailbox_apu_rpu0: ipi_mailbox@0 {
> + compatible = "xlnx,zynqmp-ipi-mailbox";
> + reg = <0 0xff990400 40>;
> + reg-names = "apu-rpu0";
> + ipi-smc-fid-base = <0x1010>;
> + method = "smc";
> + #mbox-cells = <1>;
> + interrupt-parent = <&gic>;
> + interrupts = <0 35 4>;
> + };
> + ipi_mailbox_apu_rpu1: ipi_mailbox@1 {
> + compatible = "xlnx,zynqmp-ipi-mailbox";
> + reg = <0 0xff990440 40>;
> + reg-names = "apu-rpu1";
> + ipi-smc-fid-base = <0x1020>;
> + method = "smc";
> + #mbox-cells = <1>;
> + interrupt-parent = <&gic>;
> + interrupts = <0 35 4>;
> + };

Why do you need the above 2 ? They don't look like 2 controller blocks.
You just need to represent single mailbox controller.

--
Regards,
Sudeep